HIERARCHICAL-MODELS, RETICULATE EVOLUTION AND THE INEVITABILITY OF PARAPHYLETIC SUPRASPECIFIC TAXA

A phylogenetic tree can be subdivided according to a monophyletic hier archical model, in which only monophyletic units figure, or according to a ''Linnaean'' hierarchical model in which both mono- and paraphyle tic units occur. Most present-day phylogeneticists try to fit the mono phyletic model within the set of nomenclatural conventions that fit th e Linnaean model. However, the two models are intrinsically incongruen t. The monophyletic model requires a system of classification of its o wn, at variance with currently accepted conventions. Since, however, t he monophyletic model is unable to cope with reticulate evolutionary r elationships, it is unsuited for the classification of nature. The Lin naean model is to be preferred. This renders the acceptance of paraphy letic supraspecific taxa inevitable.